Feinstein, who is locked in a tough reelection fight with fellow Democrat state Sen. Kevin de Leon, used her pro-death penalty position prominently in her first Senate campaign in 1992. The tactic was designed to appeal to liberal Republicans, and the strategy worked.

Since that time, Feinstein was a consistent proponent of capital punishment. In 2004, the issue put her at odds with then-San Francisco District Attorney Kamala Harris, who opposed the death penalty. When Feinstein discovered Harris opposed the death penalty amid a contentious and high-profile case, she said she wouldn’t have endorsed Harris if she knew her position:

In 2004, Feinstein put then-San Francisco Dist. Atty. Kamala Harris on the spot by calling for the death penalty for the killer of San Francisco Police Officer Isaac Espinoza during a speech at his funeral, which both women attended.

Harris, an opponent of capital punishment who is now Feinstein’s colleague in the Senate, had declined to seek the death penalty. Feinstein described the killing as “the special circumstance called for by the death penalty law” and said at the time that she wouldn’t have endorsed Harris if she’d known Harris opposed the death penalty.

But now the two, colleagues in the Senate, are on the same page when it comes to capital punishment. What caused the change of heart for Feinstein? No one, including her staff, seems to know the answer.

Her staff said the change of heart on capital punishment went largely unnoticed because Feinstein was rarely asked about it. They could not pinpoint exactly when the shift occurred.

Feinstein’s staff claims that they have mentioned her flip-flop on the issue in letters to constituents.

“It has now become clear to me that the death penalty is being applied inconsistently,” the letter states, according to the Los Angeles Times. “There is more and more evidence that innocent people have been put to death and that the death penalty is applied arbitrarily or discriminatorily on the basis of race, gender, and geography.”

But as recently as 2013, Feinstein said she supported the death penalty, when discussing the Boston Marathon bombing.